I second what others have posted about AP horizontal would be better. However I would have to counter the hit for IPS comment. My ISP connection is cable with 500/50 Mbps and I have. USG-Pro4 with IPS Enabled with most categories enabled (way more than default). Latest firmware updates have majorly improved the performance. I see a very minimal to no hit at all for IPS nor Smart Queues for that matter.

I hit consistent 460-510 range for downloads depending on my network load at the time of the test. For uploads I use Smart Queues capped at 40mbps (80% of my capcity of 50) and its normally 36-40 for uploads.